tuned signature: remove unused;

--- a/src/Pure/Thy/latex.ML	Sun Dec 05 16:26:03 2021 +0100
+++ b/src/Pure/Thy/latex.ML	Sun Dec 05 16:46:50 2021 +0100
@@ -14,7 +14,6 @@
   val macro0: string -> text
   val macro: string -> text -> text
   val environment: string -> text -> text
-  val output_name: string -> string
   val output_ascii: string -> string
   val output_ascii_breakable: string -> string -> string
   val output_symbols: Symbol.symbol list -> string